title: Effect of distal interlock fixation in stable intertrochanteric fractures.
abstract: The objective of this study was to evaluate the torsion stiffness of locked and unlocked distal fixation of long cephalomedullary nail constructs, in both a fresh fracture and healed, stable intertrochanteric fracture model. Samples were tested in both internal and external rotation (0±3 Nm) for a duration of 10 cycles. Each femur was tested without instrumentation (intact femur), with instrumentation and no fracture (healed intertrochanteric fracture), and with instrumentation with an osteotomy creating a stable intertrochanteric fracture (fresh fracture). All specimens were instrumented with a long cephalomedullary nail. A distal interlock was placed in the dynamic position in 1 femur, and the other femur of the matched pair was left unlocked. Mean external (ER) and internal (IR) rotation stiffness for intact femurs without instrumentation (ER, 2.1±0.5 Nm/degree; IR, 2.2±0.5 Nm/degree) was statistically stiffer (P<.05 for all) compared with fresh fractured locked (ER, 1.1±0.2 Nm/degree; IR, 1.1±0.3 Nm/degree) and fresh fractured unlocked (ER, 0.9±0.3 Nm/degree; IR, 1.0±0.2 Nm/degree) samples. Similarly, healed locked (ER, 2.5±0.2 Nm/degree; IR, 2.8±0.1 Nm/degree) and healed unlocked (ER, 2.5±0.5 Nm/degree; IR, 2.4±0.3 Nm/degree) samples had statistically higher stiffness compared with fresh fractured treatments. These results suggest that the unlocked distal constructs provide similar torsional strength compared with locked fixation in these models.
authors.affiliation: Department of Orthopaedics, The Warren Alpert Medical School of Brown University, Providence, RI, USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Kane
authors.forename: Bryan
authors.initials: B
authors.lastname: Vopat
authors.forename: David
authors.initials: D
authors.lastname: Paller
authors.forename: Sarath
authors.initials: S
authors.lastname: Koruprolu
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Born
mesh_terms: D000369:Aged, 80 and over; D001858:Bone Nails; D001863:Bone Screws; D002102:Cadaver; D055119:Elastic Modulus; D019544:Equipment Failure Analysis; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods*; D006620:Hip Fractures / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D013718:Tensile Strength; D019415:Torque; D016896:Treatment Outcome